Tunable LED Spectra for Circadian Control With Stable CRI
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Solution Overview
Problem
Existing LED-based illumination products provide excessive circadian stimulation, are not tunable, and fail to maintain desirable light quality aspects such as correlated color temperature (CCT) and color rendering index (CRI) throughout their range, leading to potential health issues and inadequate adaptation to diurnal cycles.
Innovation Solution
Designing LED light sources with combinations of different emission spectra that can be tuned to vary circadian stimulation while maintaining CRI above 80 and CCT within a prescribed range, using a first and second LED emission source with specific spectral power distribution (SPD) fractions and color rendering properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If blue-primary phosphor-converted white-emitting LEDs are used, then LED-based illumination sources achieve high efficiency and long lifespan, but they provide excessive circadian stimulation compared to traditional sources
Solution Approach 1:
The illumination source is divided into multiple independent LED channels with different emission characteristics. The system includes a first LED channel emitting in a first wavelength range and a second LED channel emitting in a second wavelength range, allowing independent control of each channel's contribution to circadian stimulation while maintaining overall illumination efficiency
Solution Approach 2:
The system dynamically adjusts the emission parameters of different LED channels by varying their drive currents. By changing the current through the first and second LEDs, the system can modulate the spectral power distribution to provide varying levels of circadian stimulation while maintaining adequate illumination levels throughout the day
2Adaptability or versatility
If illumination products are made tunable to vary circadian stimulation, then health benefits can be achieved, but color rendering quality deteriorates throughout the tunable range
Solution Approach 1:
The illumination system is segmented into multiple LED channels with distinct spectral characteristics. The first LED channel provides a first spectral power distribution optimized for certain color rendering properties, while the second LED channel provides a second spectral power distribution optimized for other properties, allowing the system to maintain color rendering quality across different circadian stimulation levels
Solution Approach 2:
The system creates a composite light source by combining multiple LED emission spectra. The combined output from the first and second LEDs produces a spectral power distribution that maintains high color rendering quality (CRI > 80) across the full tunable range while enabling variable circadian stimulation levels
3Device complexity
If legacy illumination products are used, then simple design and manufacturing are maintained, but they fail to address the impact on humans with respect to diurnal or circadian cycles
Solution Approach 1:
The system transitions from static illumination to dynamic, time-varying illumination. A controller adjusts the drive currents to the first and second LEDs based on the time of day, providing high circadian stimulation in the morning and reducing it in the evening, thereby adapting to natural circadian rhythms while maintaining manageable system complexity through automated control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution allows for LED light sources that simulate a natural circadian cycle, reducing adverse health effects by varying circadian stimulation and maintaining desirable light quality, thus enhancing health and amenity.
Implementation Method 1
at least one first LED emission source having a first emission; and at least one second LED emission source having a second emission
Data Source
AI summary
Methods and apparatus for providing circadian-friendly LED light sources are disclosed. A light source is formed to include a first LED emission (e.g., one or more LEDs emitting a first spectrum) and a second LED emission (e.g., one or more LEDs emitting a second spectrum) wherein the first and second LED emissions are combined in a first ratio and in a second ratio such that while changing from the first ratio to the second ratio the relative circadian stimulation is varied while maintaining a color rendering index above 80.